U.S. Pat. No. 5,688,792 (U.S. Pat. No. 5,688,792) disclosed oxazine and thiazine oxazolidinone derivatives. The compounds are antimicrobial agents. Among them linezolid, chemically N-[[(5S)-3-[3-fluoro-4-(4-morpholinyl)phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide is the most important antibacterial agent. Linezolid is represented by the following structure:

Processes for preparation of linezolid were described in U.S. Pat. No. 5,837,870, WO 99/24393, WO 95/07271, J. Med. Chem. 39(3), 673-679, 1996 and Tetrahedron Lett., 40(26), 4855, 1999.
According to prior art processes, the 5-hydroxymethyl substituted oxazolidinones are converted to the corresponding 5-aminomethyl substituted oxazolidinones, key intermediates in the production of oxazolidinone antibacterial pharmaceuticals.
The prior art processes for preparing 5-aminomethyl substituted oxazolidinones are associated with many drawbacks. For instant in the preparation of linezolid, WO 95/07271 uses butyl lithium at very low temperature (−78° C.) and WO 99/24393 uses phosgene gas. It is known that the handling of butyl lithium and phosgene gas are difficult and the person skilled in the art appreciate a process that produces the product in good yield avoiding the ‘difficult to handle’ reagents.
We have discovered a novel process for preparation of 5-aminomethyl substituted oxazolidinone key intermediates using novel intermediates. The novel process solve the drawbacks associated with the prior processes and so, commercially viable for preparing these and related compounds.